There has arisen in recent years processes for imparting a soft, worn look to new clothing, in particular denim jeans. This is related to the laundering industry and is a wet process known as "stone washing." Consumers will pay a significant premium for clothes have a soft, worn look. A number of methods have been developed for washing new garments and fabrics to cause them to have the desired feel and appearance. Among the methods presently employed for stone washing include washing with large pumice stones, usually 1/2 to 4 inches in diameter. These large stones circulate in a washing machine during the wash cycle and cause the garments to abrade and soften. It can be appreciated that this sometimes creates wear to the garments and makes them unsuitable for sale. Volcanic rock is usually more glassy than pumice and is sometimes used in a similar way. U.S. Pat. Nos. 4,575,887 and 4,750,227 represent this type of wet process.
Manufactured substitutes for the natural pumice and volcanic rock have been tried. U.S. Pat. No. 5,359,745 teaches a briquette formed of glass and calcium carbonate which is then fired to produce a foamed glass briquette which substitutes for the pumice stone. Synthetic polymer composition material has also been taught to be useful in creating a briquette. In U.S. Pat. No. 5,367,734, polyvinyl chloride is filled with abrasive aluminum trihydrate to provide a resilient, yet abrasive pellet. This structure is thought to be less likely to pound holes into the garment. Similarly, U.S. Pat. No. 5,093,948 teaches the use of an elastomer rubber ball made of polybutadiene without any abrasive. Many different materials and shapes have been used as the abrasive medium in stone washing of garments to achieve alterations in the surface and texture of the garment.
There are many different abrasive mediums that are commonly used in various processes, including wood, walnut shells, sawdust, granite, various metals, limestone, ceramic beads, dry ice, nylon, rubber and synthetic rubberized abrasive. These abrasive mediums are used in tumblers or barrels, wet or dry, depending upon the process involved. It is believed that all presently used abrasive medium is a consumable product because the surface of the medium changes its characteristics with wear, and the medium itself wears out through the abrading action on the workpieces. This limits the usage of many common mediums which are used in food product applications, such as skin-peeling processes for potatoes, nuts or carrots. In pedicure processes, dead skin (callous) is removed by abrading with a pumice stone. This process takes place in a water bath. Therefore, it is desirable to employ a pedicure abrasive medium which has a density less than 1 so that it floats on the water. Sterilization of pumice stone is difficult because it has deep cavities and porosity which are not present in the presently disclosed abrasive. The disclosed abrasive medium can be readily cleansed of unwanted bacteria and viruses.
There is need for an abrasive medium which is of long wear life and which is of preselected density so as to properly interact with the workpiece.